The present invention is generally directed to toner processes, and more specifically, to aggregation and coalescence processes for the preparation of toner compositions. In embodiments, the present invention is directed to the economical chemical in situ preparation of liquid toners without the utilization of the known pulverization and/or classification methods for the preparation of the solids component of toner resin and pigment, and wherein in embodiments toner compositions with an average volume diameter of from about 1 to about 10 and preferably from 1 to about 3 microns, and narrow GSD of, for example, from about 1.16 to about 1.26 as measured on the Coulter Counter can be obtained and are dispersed in a suitable liquid development carrier fluid, such as a mineral oil, and the like. The resulting liquid toners can be selected for known electrophotographic imaging, printing processes, including color processes, and lithography. In embodiments, the present invention is directed to a process comprised of dispersing a pigment, and optionally toner additives like a charge control agent or additive in an aqueous mixture containing an ionic surfactant in an amount of from about 0.5 percent (weight percent throughout unless otherwise indicated) to about 10 percent, and shearing this mixture with a latex or emulsion mixture comprised of suspended submicron resin particles of from, for example, about 0.01 micron to about 2 microns in volume average diameter in an aqueous solution containing a counterionic surfactant in amounts of from about 1 percent to about 10 percent with opposite charge to the ionic surfactant of the pigment dispersion, and nonionic surfactant in amounts of from about 0 percent to about 5 percent, thereby causing a flocculation of resin particles, pigment particles and optional charge control agent, followed by heating at about 5 to about 40.degree. C. below the resin Tg and preferably about 5 to about 25.degree. C. below the resin Tg while stirring of the flocculent mixture, which is believed to form statically bound aggregates of from about 1 micron to about 10 microns in volume average diameter comprised of resin, pigment and optionally charge control particles, and thereafter heating the formed bound aggregates about above the Tg (glass transition temperature) of the resin, and subsequently forming a liquid toner by for example dispersing the formed toner in a hydrocarbon fluid. The size of the aforementioned aggregated particles can be controlled by adjusting the temperature in the below the resin Tg heating stage. An increase in the temperature causes an increase in the size of the aggregated particle. This process of aggregating submicron latex and pigment particles is kinetically controlled, that is the temperature increases the process of aggregation. The higher the temperature during stirring the quicker the aggregates are formed, for example from about 2 to about 10 times faster in embodiments, and the latex submicron particles are picked up more quickly. The temperature also controls in embodiments the particle size distribution of the aggregates, for example the higher the temperature the narrower the particle size distribution, and this narrower distribution can be achieved in, for example, from about 0.5 to about 24 hours and preferably in about 1 to about 3 hours time. Heating the mixture about above or in embodiments equal to the resin Tg generates toner particles with, for example, an average particle volume diameter of from about 1 to about 25 and preferably 10 microns. It is believed that during the heating stage, the components of aggregated particles fuse together to form composite toner particles. In another embodiment thereof, the present invention is directed to an in situ process comprised of first dispersing a pigment, such as HELIOGEN BLUE.TM. or SUNSPERSE.TM. or FLEXVERSE.TM. BLUE, magenta, yellow, or black in an aqueous mixture containing a cationic surfactant, such as benzalkonium hloride (SANIZOL B-50.TM.), utilizing a high shearing device, such as a Brinkmann Polytron, microfluidizer or sonicator, thereafter shearing this mixture with a latex of suspended resin particles, such as poly(styrene butadiene acrylic acid), poly(styrene butylacrylate acrylic acid) or PLIOTONE.TM., a poly(styrene butadiene), and which particles are, for example, of a size ranging from about 0.01 to about 0.5 micron in volume average diameter as measured by the Brookhaven nanosizer in an aqueous surfactant mixture containing an anionic surfactant, such as sodium dodecylbenzene sulfonate, for example NEQGEN R.TM. or NEOGEN SC.TM., and a nonionic surfactant such as alkyl phenoxy poly(ethylenoxy)ethanol, or example IGEPAL 897.TM. or ANTAROX 897.TM., thereby resulting in a flocculation, or heterocoagulation of the resin particles with the pigment particles; and which, on further stirring for about 0.5 to about 3 hours while heating, for example, from about 35 to about 45.degree. C., results in the formation of statically bound aggregates ranging in size of from about 0.5 micron to about 10 microns in average diameter size as measured by the Coulter Counter (Microsizer II), where the size of those aggregated particles and their distribution can be controlled by the temperature of heating, for example from about 5 to about 25.degree. C. below the resin Tg, and where the speed at which toner size aggregates are formed can also be controlled by the temperature. Thereafter, heating from about 5 to about 50.degree. C. above the resin Tg provides for particle fusion or coalescence of the polymer and pigment particles; followed by optional washing with, for example, water to remove surfactant, and drying whereby toner particles comprised of resin and pigment with various particle size diameters can be obtained, such as from 1 to about 20, and preferably 12 microns in average volume particle diameter. The aforementioned toners are especially useful for the development of colored images with excellent line and solid resolution, and wherein substantially no background deposits are present.
Numerous processes are known for the preparation of dry toners, such as, for example, conventional processes wherein a resin is melt kneaded or extruded with a pigment, micronized and pulverized to provide toner particles with an average volume particle diameter of from about 9 microns to about 20 microns, and with broad geometric size distribution of from about 1.4 to about 1.7. In these processes, it is usually necessary to subject the aforementioned toners to a classification procedure such that the geometric size distribution of from about 1.2 to about 1.4 is attained. Also, in the aforementioned conventional process, low toner yields after classifications are obtained. Generally, during the preparation of toners with average particle size diameters of from about 11 microns to about 15 microns, toner yields range from about 70 percent to about 85 percent after classification. Additionally, during the preparation of smaller sized toners with particle sizes of from about 7 microns to about 11 microns, lower toner yields can be obtained after classification, such as from about 50 percent to about 70 percent. With the processes of the present invention in embodiments, small average particle sizes of, for example, from about 2 microns to about 9 microns, and preferably 3 microns, are attained without resorting to classification processes, and wherein narrow geometric size distributions are attained, such as from about 1.16 to about 1.30, and preferably from about 1.16 to about 1.25. High toner yields are also attained such as from about 90 percent to about 98 percent in embodiments of the present invention. In addition, by the toner particle preparation process of the present invention in embodiments, small particle size toners of from about 3 microns to about 7 microns can be economically prepared in high yields, such as from about 90 percent to about 98 percent by weight based on the weight of all the toner material ingredients, such as toner resin and pigment.
There is illustrated in U.S. Pat. No. 4,996,127 a toner of associated particles of secondary particles comprising primary particles of a polymer having acidic or basic polar groups and a coloring agent. The polymers selected for the toners of the '127 patent can be prepared by an emulsion polymerization method, see for example columns 4 and 5 of this patent. In column 7 of this '127 patent, it is indicated that the toner can be prepared by mixing the required amount of coloring agent and optional charge additive with an emulsion of the polymer having an acidic or basic polar group obtained by emulsion polymerization. Also, see column 9, lines 50 to 55, wherein a polar monomer, such as acrylic acid, in the emulsion resin is necessary, and toner preparation is not obtained without the use, for example, of acrylic acid polar group, see Comparative Example I. In U.S. Pat. No. 4,983,488, there is disclosed a process for the preparation of toners by the polymerization of a polymerizable monomer dispersed by emulsification in the presence of a colorant and/or a magnetic powder to prepare a principal resin component, and then effecting coagulation of the resulting polymerization liquid in such a manner that the particles in the liquid after coagulation have diameters suitable for a toner. It is indicated in column 9 of this patent that coagulated particles of 1 to 100, and particularly 3 to 70 are obtained. This process is thus directed to the use of coagulants, such as inorganic magnesium sulfate, which results in the formation of particles with a wide GSD. Furthermore, the '488 patent does not, it appears, disclose the process of counterionic, for example controlled aggregation is obtained by changing the counterionic strength, flocculation. Similarly, the aforementioned disadvantages, for example poor GSD is obtained hence classification is required resulting in low toner yields, are illustrated in other prior art, such as U.S. Pat. No. 4,797,339, wherein there is disclosed a process for the preparation of toners by resin emulsion polymerization, wherein similar to the '127 patent certain polar resins are selected.
Certain liquid developers and processes thereof are known. A latent electrostatic image can be developed with toner particles comprised of solids of resin, pigment, and charge adjuvant dispersed in an insulating nonpolar liquid, and charge director. A latent electrostatic image may be generated by providing a photoconductive layer with a uniform electrostatic charge and subsequently discharging the electrostatic charge by exposing it to a modulated beam of radiant energy. Other methods are also known for forming latent electrostatic images such as, for example, providing a carrier with a dielectric surface and transferring a preformed electrostatic charge to the surface. After the latent image has been formed, it is developed by colored toner particles dispersed in a nonpolar liquid. The image may then be transferred to a receiver sheet.
Liquid developers can comprise a thermoplastic resin, colorant like pigment or dye, and a dispersant nonpolar liquid. The colored toner particles are dispersed in a nonpolar liquid which generally has a high volume resistivity in excess of 10.sup.9 ohm-centimeters, a low dielectric constant, for example below 3.0, and a high vapor pressure. Generally, the toner particles are less than 10 microns (.mu.m) average by area size as measured by the Horiba Capa 500 or 700 particle sizers.
Since the formation of images depends, for example, on the difference of the charge between the toner particles in the liquid developer and the latent electrostatic image to be developed, it has been found desirable to add a charge director compound and charge adjuvants, which increase the magnitude of the charge, such as polyhydroxy compounds, amino alcohols, polybutylene succinimide compounds, aromatic hydrocarbons, metallic soaps, and the like to the liquid developer comprising the thermoplastic resin, the nonpolar liquid and the colorant.
U.S. Pat. No. 5,019,477, the disclosure of which is totally incorporated herein by reference, discloses a liquid electrostatic developer comprising a nonpolar liquid, thermoplastic resin particles, and a charge director. The ionic or zwitterionic charge directors may include both negative charge directors, such as lecithin, oil-soluble petroleum sulfonate and alkyl succinimide, and positive charge directors, such as cobalt and iron naphthanates. The thermoplastic resin particles can comprise a mixture of (1) a polyethylene homopolymer or a copolymer of (i) polyethylene and (ii) acrylic acid, methacrylic acid or alkyl esters thereof, wherein (ii) comprises 0.1 to 20 weight percent of the copolymer; and (2) a random copolymer of (iii) selected from the group consisting of vinyl toluene and styrene, and (iv) selected from the group consisting of butadiene and acrylate.
U.S. Pat. No. 5,030,535 discloses a liquid developer composition comprising a liquid vehicle, a charge control additive and toner particles. The toner particles may contain pigment particles and a resin selected from the group consisting of polyolefins, halogenated polyolefins and mixtures thereof. The liquid developers are prepared by first dissolving the polymer resin in a liquid vehicle by heating at temperatures of from about 80.degree. C. to about 120.degree. C., adding pigment to the hot polymer solution and attriting the mixture, and then cooling the mixture so that the polymer becomes insoluble in the liquid vehicle, thus forming an insoluble resin layer around the pigment particles, may be selected from known thermoplastics, including fluoropolymers.
Moreover, in U.S. Pat. No. 4,707,429 there are illustrated, for example, liquid developers with an aluminum stearate charge additive. Liquid developers with charge directors are also illustrated in U.S. Pat. No. 5,045,425.
In U.S. Pat. No. 5,306,591, there is disclosed a liquid developer comprised of thermoplastic resin particles, a charge director, and a charge adjuvant comprised of an imine bisquinone; and U.S. Pat. No. 5,308,731 discloses a liquid developer comprised of a liquid, thermoplastic resin particles, a nonpolar liquid soluble charge director, and a charge adjuvant comprised of a metal hydroxycarboxylic acid.
The disclosures of each of the U.S. Pat. Nos. mentioned herein are totally incorporated herein by reference.
In U.S. Pat. No. 5,407,775, the disclosure of which is totally incorporated herein by reference, there is illustrated a liquid developer comprised of a liquid, thermoplastic resin particles, a nonpolar liquid soluble charge director comprised of a zwitterionic quaternary ammonium block copolymer wherein both cationic and anionic sites contained therein are covalently bonded within the same polar repeat unit in the quaternary ammonium block copolymer.
In U.S. Pat. No. 5,459,007, the disclosure of which is totally incorporated herein by reference, there is illustrated a liquid developer comprised of a liquid, thermoplastic resin particles, a nonpolar liquid soluble charge director comprised of an ionic or zwitterionic quaternary ammonium block copolymer ammonium block copolymer, and wherein the number average molecular weight thereof of the charge director is from about 70,000 to about 200,000.
In U.S. Pat. No. 5,290,654, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of, for example, dry toners comprised of dispersing a polymer solution comprised of an organic solvent and a polyester, and homogenizing and heating the mixture to remove the solvent and thereby form toner composites. Additionally, there is illustrated in U.S. Pat. No. 5,278,02, the disclosure of which is totally incorporated herein by reference, a process for the preparation of a toner composition comprising:
(i) preparing a latex emulsion by agitating in water a mixture of a nonionic surfactant, an anionic surfactant, a first nonpolar olefinic monomer, a second nonpolar diolefinic monomer, a free radical initiator and a chain transfer agent; PA1 (ii) polymerizing the latex emulsion mixture by heating from ambient temperature to about 80.degree. C. to form nonpolar olefinic emulsion resin particles of volume average diameter of from about 5 nanometers to about 500 nanometers; PA1 (iii) diluting the nonpolar olefinic emulsion resin particle mixture with water; PA1 (iv) adding to the diluted resin particle mixture a colorant or pigment particles, and optionally dispersing the resulting mixture with a homogenizer; PA1 (v) adding a cationic surfactant to flocculate the colorant or pigment particles to the surface of the emulsion resin particles; PA1 (vi) homogenizing the flocculated mixture at high shear to form statically bound aggregated composite particles with a volume average diameter of less than or equal to about 5 microns; PA1 (vii) heating the statically bound aggregate composite particles to form nonpolar toner sized particles; PA1 (viii) halogenating the nonpolar toner sized particles to form nonpolar toner sized particles having a halopolymer resin outer surface or encapsulating shell; and PA1 (ix) isolating the nonpolar toner sized composite particles. PA1 In U.S. Pat. No. 5,346,797, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner compositions comprising PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment, an ionic surfactant and optionally a charge control agent; PA1 (ii) shearing the pigment dispersion with a latex mixture comprised of a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, a nonionic surfactant and resin particles, thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin and charge control agent to form electrostatically bounded toner size aggregates; and PA1 (iii) heating the statically bound aggregated particles above the resin Tg to form said toner composition comprised of polymeric resin, pigment and optionally a charge control agent. PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment, an ionic surfactant in amounts of from about 0.5 to about 10 percent by weight of water, and an optional charge control agent; PA1 (ii) shearing the pigment dispersion with a latex mixture comprised of a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, a nonionic surfactant and resin particles, thereby causing a flocculation or heterocoagulation of the formed particles of pigment, resin and charge control agent; PA1 (iii) stirring the resulting sheared viscous mixture of (ii) at from about 300 to about 1,000 revolutions per minute to form electrostatically bound substantially stable toner size aggregates with a narrow particle size distribution; PA1 (iv) reducing the stirring speed in (iii) to from about 100 to about 600 revolutions per minute and subsequently adding further anionic or nonionic surfactant in the range of from about 0.1 to about 10 percent by weight of water to control, prevent, or minimize further growth or enlargement of the particles in the coalescence step (iii); and PA1 (v) heating and coalescing from about 5 to about 50.degree. C. above about the resin glass transition temperature, Tg, which resin Tg is from between about 45 to about 90.degree. C. and preferably from between about 50 and about 80.degree. C., the statically bound aggregated particles to form said toner composition comprised of resin, pigment and optional charge control agent; and PA1 (vi) optionally washing the particles of step (v) with water to remove the surfactants followed by drying either by a freeze dryer or fluid bed drying. PA1 (i) preparing a pigment dispersion, which dispersion is comprised of a pigment, and an ionic surfactant; PA1 (ii) shearing said pigment dispersion with a latex or emulsion blend comprised of a nonionic surfactant, resin, and a counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant and optionally adding further anionic, or nonionic surfactant to stabilize the aggregates obtained in (iii); PA1 (iii) heating the above resulting sheared or aqueous blend below about, or about equal to, the glass transition temperature (Tg) of the resin to form toner size aggregates with a narrow particle size distribution; PA1 (iv) heating said bound aggregates about equal to, or above about the Tg of the resin to form toner size particles in an aqueous medium, and which particles possess a narrow particle size distribution; and PA1 (v) separating from the aqueous medium toner particles of resin and pigment, and dispersing said toner particles in a carrier fluid. PA1 (i) preparing a pigment dispersion in a water, which dispersion is comprised of a pigment, an ionic surfactant, and optionally a charge control agent; PA1 (ii) shearing the pigment dispersion with a latex mixture comprised of polymeric or resin particles in water and counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, and a nonionic surfactant; PA1 (iii) heating the resulting homogenized mixture below about the resin Tg at a temperature of from about 35 to about 50.degree. C. (or 5 to 20.degree. C. below the resin Tg) thereby causing flocculation or heterocoagulation of the formed particles of pigment, resin and charge control agent to form electrostatically bounded toner size aggregates; PA1 (iv) adding further anionic, or non ionic surfactant to stabilize the aggregates obtained in (iii), followed by reducing the stirring speeds to about 100 to 600 rpm; and PA1 (v) heating to, for example, from about 60 to about 95.degree. C. the statically bound aggregated particles of (iv) to form a composition comprised of polymeric resin and pigment; optionally washing the formed product with water to remove the surfactant; drying and subsequently dispersing the formed product of solids of resin, pigment, and additive in a hydrocarbon fluid. The liquid developers may contain charge adjuvants, or charge additives, and charge directors. PA1 (i) preparing a pigment dispersion in water, which dispersion is comprised of a pigment, an ionic surfactant and optionally a charge control agent by mixing at high speeds of about 1,000 to about 3,000 rpms using a high shear device, such as a polytron, or by a microfluidizer, or by an ultrasonic probe; PA1 (ii) shearing the pigment dispersion (i) with a latex mixture comprised of polymeric or resin particles in water and counterionic surfactant with a charge polarity of opposite sign to that of said ionic surfactant, and a nonionic surfactant at speeds of 2,000 to 15,000 rpm and preferably at speeds of 3,000 to 10,000 for a period of 1 to 30 minutes and preferably 2 to 15 minutes; PA1 (iii) heating the resulting homogenized mixture below about the resin Tg at a temperature of from about 35 to about 50.degree. C. (or 5 to 20.degree. C. below the resin Tg) thereby causing flocculation or heterocoagulation of the formed particles of pigment, resin and charge control agent to form toner size aggregates of 2 to 20 microns and preferably in the range of 3 to 10 microns with a GSD in the range of 1.16 to 1.30 and preferably in the range of 1.16 to 1.25; and PA1 (iv) adding further anionic, or nonionic surfactant to stabilize the aggregates obtained in (iii), followed by reducing the stirring speeds to about 50 to 600 rpm and preferably in the range of 100 to 300 rpm; PA1 (v) heating to, for example, from about 60 to about 95.degree. C. the statically bound aggregated particles of (iv) to form a composition comprised of polymeric resin and pigment; followed by optionally washing the formed product with water to remove the surfactant; followed by drying followed by dispersing the formed product in a hydrocarbon fluid. The liquid developers may contain charge adjuvants, or charge additives, and charge directors.
In U.S. Pat. No. 5,403,693, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of toner compositions with controlled particle size comprising: